Fiona Stanley Hospital will cost $850 million a year to run, according to the health official overseeing the project.
Dr David Russell-Weisz, chief executive of the hospital's commissioning phase, has warned that the $2 billion cost of building the Murdoch hospital is only the start of what will be a massive budget demand.
Writing in the Australian Medical Association WA magazine Medicus this month, he said the public health system was already responsible for a quarter of the State Budget.
"Even if it grows one to two per cent above this, as a community we will be faced with making some very tough decisions about what we want our health system to be and do, and the likely expense of those decisions," he said.
"We need to start having that discussion now and not when we suddenly find ourselves in an unsustainable, precarious funding position.
"We know the future carries with it enormous health demands, with an ageing population and an increase in chronic health conditions."
Dr Russell-Weisz was recruited to the hospital project a year ago in response to mounting concerns about long delays to the opening of all its departments, some of them linked to information technology issues.
He had previously been involved in other hospital projects, including the expansion of Joondalup Health campus and the redevelopment of the QEII Medical Centre site.
Because of Government delays in developing IT systems and hiring staff, Health Minister Kim Hames confirmed six months ago that Fiona Stanley Hospital would not start taking patients until October next year, with full operations delayed until April 2015.
Dr Russell-Weisz said in the magazine that it was the most complicated hospital development in Australia, and such a project would normally take between three and 18 months to fully open. The Murdoch hospital would be done in six months.
"We are making steady progress but there are still challenges and a huge volume of work ahead," he said.